Paris’ catacombs, underground passages full of neatly stacked human bones, have been temporarily closed to the public after being vandalized.

A spokeswoman for the Paris prosecutor’s office would not go into detail on the extent of the vandalism, which took place over the weekend, but said that the site would be closed because in its current state it was hazardous to visitors. According to the AP, a photo in a Paris newspaper showed “bones and skulls scattered along the walking paths”. There was no word on when the catacombs would reopen, but as they are a major tourist attraction visited by over 250,000 people each year, it seems that the city would do its best to clean the mess and repair any damage as soon as possible.

The catacombs open to the public are just one part of an 186-mile network underneath the city. The bones of over 6 million Parisians are contained here, having been moved to the site in the 18th and 19th centuries after the city’s cemeteries became overcrowded and contributed to the spread of disease.